Palaeomagnetism of stalagmite deposits

Abstract

VARIOUS sedimentary deposits have recently been studied with the aim of producing geomagnetic field curves representing the Brunhes epoch. Unfortunately the magnetic recording process tends to be subject to several depositional and post-depositional errors and in the light of these Watkins¹, Verosub² and Verosub and Banerjee³ have reviewed many of the claims that have been made for secular variation and anomalous field behaviour. The corresponding age data, provided by ¹⁴C, uranium series disequilibrium and other methods may also suffer from such errors as bioturbation and migration of radionuclides. It has been shown that most speleothems (here stalagmites ana flowstones) may be dated by uranium series methods to an age limit of 350,000 yr BP⁴. With the aim of finding an alternative continuous magnetic record we have studied the natural remanent magnetism (NRM) and ages of speleothems from the Canadian Rockies, the UK and elsewhere. We report here briefly on two of them and in greater detail on a third.